Precision inertial navigation systems typically require concentric sets of ball bearing supported gimbals which allow instruments to freely rotate in flight maneuvers and allow them to be manipulated for calibration. The embodiments of the previously referenced '6540 Application, which is herein incorporated by reference, eliminate the need for gimbals and ball bearings by supporting the inertial sensor assembly with a spherically shaped gas bearing. The gas bearing allows rotation of the inertial sensor assembly in all axes with no wear due to contact between rotating surfaces. However, because physical contact with the freely rotating inertial sensor assembly is undesirable, the need arises to sense the motion of the inertial sensor assembly without physical contact between the sensor and the assembly.
An optical computer mouse is one example of a low cost sensor that detects relative movement with respect to a flat surface without the need for physical contact between the mouse and the surface. The optical mouse system includes an image acquisition system (IAS) and a digital signal processor (DSP). The IAS forms an image of the microscopic textural features of the surface below the sensor. A sequence of these images is taken quickly so that the sequential pictures overlap. The images are processed by the DSP to determine the relative direction and distance of motion between the surface and the sensor. The DSP further produces a stream of relative delta-x and delta-y displacement values along the x and y axis. The resulting displacement data is provided by the output of the mouse to the computer. The data is used by the computer to relocate an on-screen pointer in coordination with movement of the mouse.
The algorithms translating mouse movement into cursor movement are nonlinear in order to aid the user with quickly selecting the desired object on the monitor. A human viewing the computer screen and operating the mouse provides the required feedback loop to ensure that cursor controlled by the mouse is accurately positioned on the screen. Precise calculations of the exact distance, direction and velocity of relative motion between the mouse sensor and surface are not necessary for this application and thus are not determined. For these reasons, the optical navigation system applied by optical computer mice is inadequate in applications where the precise direction and distance of displacement and velocity of an object is required.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for contact free precision motion detection system.